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Re^3: How to freeze rotation of the atoms frozen with IFRZAT keyword

Alex Granovsky

Dear Evgeniy,

I'm sorry for long delay with my reply.

Imposing multiple partially dependent restrictions on a part of a
molecule generally decreases the quality of generated coordinates
and is usually not recommended. You may need to decrease DXMAX
and TRMAX in $statpt to, say, 0.05 or so and increase FMAXT to 100
or so.

Kind regards,

On Tue Jan 19 '16 6:50pm, GrEv wrote
>Dear Alex,

>Thanks for your reply.
>Concerning my question, I would use the keyword IFREEZ to completely
>freeze the atoms, however when I do so the geometry optimization stops
>after a few steps with the error that the gradient is beyond the maximum.
>During these few steps the optimization procedure somehow leads to
>increasing the gradient instead of decreasing it. Do you have an idea
>why this happens and how one can cure this.

>Best wishes,

>On Sun Jan 17 '16 5:26pm, Alex Granovsky wrote
>>Dear Evgeniy,

>>no, this is impossible.

>>Kind regards,
>>On Thu Jan 14 '16 7:51pm, GrEv wrote
>>>Dear All,

>>>I would like to freeze atoms completely, avoiding use of the keyword IFREEZ.
>>>There is the keyword IFRZAT, which freezes all the distances between
>>>the specified atoms. However, the atoms frozen with IFRZAT still can rotate as a whole
>>>with respect to the other atoms. I am wondering how one can suppress also
>>>this degree of freedom. (For example, one could freeze the distance from the origin to
>>>the atoms specified in IFRZAT. Is that possible?)

>>>Many thanks!


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